This invention relates to a means for threading a tendon end through an enclosed space. More particularly, it relates to a means for threading the end of a severed flexor tendon through its associated sheath in the hand.
Tendons which bend the human finger are called flexor tendons. Each finger has two flexor tendons, which arise from sublimis and profundus muscles in the forearm. The sublimis flexor divides into a Y and its distal ends are attached to a bone in the finger. The profundus flexor passes through the Y division of the sublimis and its distal end is attached to the most distal bone in the finger. For simplification, the flexor tendons in each finger will normally be referred to as a single tendon unless otherwise indicated. A simplified illustration of the flexor tendon in a finger is set forth in FIG. 1.
FIG. 1 shows the human finger 10 with parts of the skin and flesh removed. Flexor tendon 12 arises from muscles in the forearm 14 and is connected to bones 16 and 18 in the finger. The connection places to the bones are generally points 20, 22, and 24. Tendon 12 passes through substantially hollow tendon sheath 26 which includes a plurality of pulleys 28 through 32. The pulleys approximate the tendons close to the bones and when the finger is flexed the pulleys provide strong mechanical advantage for action of the flexor tendons on the bones in addition to preventing "bowstringing" of the flexor tendons away from the bones.
When the flexor tendon is severed because of a traumatic injury to the finger such as, for example, a deep cut, it has a tendency to retract out of the finger area into the palm area 13 because of muscle tension on the tendon end. A typical post trauma retracted, coiled up flexor tendon is shown in FIG. 3. In order for the surgeon to repair the tendon, it is necessary to thread the tendon back through the sheath. This has proved to be very difficult and almost impossible without doing damage to the tendon itself or the sheath, part of which is a thin membrane, and its fibrous pulleys. The problem is exacerbated when only one of the flexor tendons is severed, in particular the profundus tendon, whereby damage to the intact sublimis tendon must be avoided during re-threading.
Facilitation of tendon end passage through the sheath and other spaces, such as holes in the bone will speed surgical repair and reconstruction. Various methods have been utilized to attempt to thread the tendon back through the sheath. In one method, the free end of the tendon is sutured to one end of a solid silastic rod. The solid rod is passed through the sheath, pulling the tendon along through the sheath to the place of repair. However, it has been found that the end of the tendon quite often would bind up on the pulleys, causing damage to the tendon end, pulleys, or, in the case where only one of the tendons was severed, the intact tendon was damaged. Furthermore, the thin membrane part of the sheath was often damaged. The damage normally occurred because it is nearly impossible to abut the end of the tendon against the end of the rod without leaving an overhang of the tendon end or suture material, causing snags.
Rigid metal tendon passer rods which utilized teeth in jaws to grip the end of the tendon are also currently available. However, those metal rods are too rigid to readily pass through the sheath and the teeth often damage the tendon. Furthermore, the space required to open the jaws is not available in many circumstances.
In some cases, it has been proposed to totally replace the flexor tendon with a prosthesis, an example of which is disclosed in U.S. Pat. No. 3,613,120, issued to McFarland. However, such a radical approach to repairing a severed tendon is highly undesirable and has proven unsuccessful.